15-year-old girl and boyfriend stabbed mother and daughter to death - then watched four Twilight films

A 15-year-old girl is facing a life sentence in a UK court after being found guilty of murdering a mother and daughter who were stabbed through the throat in a “senseless and unprovoked” attack.

The teenager, who cannot be named because of her age, had claimed a mental disorder diminished her responsibility for the killings of dinner lady Elizabeth Edwards and 13-year-old Katie Edwards.

But a five-day trial at Nottingham Crown Court heard that the schoolgirl was not suffering from a mental illness when she and her boyfriend planned the killings “to the letter” when they were both aged 14.

Tributes left outside a house in Spalding (Chris Radburn/PA)

The girl, who remained composed in the dock, and her boyfriend, also now 15, are thought to be the youngest defendants to be convicted of double murder in a British court.

After the verdicts were delivered, Justice Haddon-Cave said it had been an “exceptional case by any standards” and praised the quiet dignity of family members who sat through the trial.

Jurors were told that the sweethearts – also believed to be the youngest couple to be convicted of murder – shared a bath, had sex, and watched four vampire-themed Twilight films after the killings in Spalding, Lincolnshire, last April.

At the start of the hearing, prosecutor Peter Joyce QC said the victims were stabbed a total of 10 times in a “cold, calculated and callous” pre-planned attack at their home.

Knife used by the teenage killers (Lincolnshire Police/PA)

In police interviews and assessments with psychiatrists, the female defendant described the killings as “a breeze” and gave a horrifying account of blood being spattered on a wall and her boyfriend’s face and hands.

In lengthy admissions to police, the schoolgirl said she and her boyfriend had planned the killings after a conversation which began with a joke suggestion of committing a murder.

After the killings, the girl said, her boyfriend “seemed fine” and they took a bath for about 20 minutes, opting not to follow their plan and take their own lives.

Consultant forensic psychiatrist Dr Philip Joseph told the trial he believed the couple’s “intense, toxic” relationship was the primary reason for the killings.